Software Musings

The Cold War

Posted on: 07/01/2009

Two things have been niggling at me for a week or so. I was thinking about Anaximander’s opposites at war with one another: hot and cold, wet and dry and so on. The thought of someone living in Miletus 2500 years ago realising that “wet” and “dry” are somehow ends of a spectrum does not surprise me: presumably he saw clothes drying in the wind and water evaporating from puddles.

Today we think of hot and cold as “opposites” in some sense without giving it a great deal of thought: we associate cold with low numbers on the thermometer and hot with high numbers. But what about someone living in Miletus (average yearly temperature span only 18 Cdeg spread gently over 6 months), 2200 years before the first thermometer, 2300 years before we gained a reasonable understanding of the distinction between heat and temperature and 2400 years before the first refrigerator? I can’t see how hot and cold would be obvious ends of the same spectrum. I would have been less surprised to see “cold” at one end and, say, “soft” at the other (since colder things tend to be stiffer).

As I understand it, the only practical experiment that Anaximader carried out was to demonstrate by blowing on his hand that compressed air is cooler than non-compressed air. A totally erroneous result based on ignoring the cooling effect of the evaporation of sweat from his hand.

This raises two questions that have been niggling at me:

  1. What led Anaximader to believe that “hot” and “cold” were opposites?
  2. Did we develop a temperature scale which has cold things at one end and hot things at the other because we saw “hot” and “cold” as opposites or is that scale natural in some way?

On an unrelated note, I also learned recently that Celsius designated the freezing point of water as 100 degrees and the boiling point as 0 degrees when he introduced his scale. This might indicate that at least our association of “hotter” with larger numbers on the thermometer is fairly recent.


3 Responses to "The Cold War"

“I can’t see how hot and cold would be obvious ends of the same spectrum.”

South of Miletus, almost within sight of the ancient Lycian city of Patara, there are mountains that hold snow throughout the year, and from whose sides, icy-cold water is directed in channels to irrigate the hot, dry plains below. In stretches where the water flows less swiftly, it warms quickly in the sun and, as one paddles, one can wade from the tepid shallows into the chilly depths quite easily. Similarly, one’s drinking water (or wine, if preferred), which has become almost hot, through being carried on one’s pack in a metal bottle, can quickly be cooled by placing it in the same channels or, if one is higher up, by burying it for a while in the snow. At night, under a clear, starry sky, frost forms on one’s tent even in summer, and it is only as the morning sun’s hot presence becomes felt that the coldness of the night can be eventually dispelled.

That Anaximander was familiar with things that were cold (by room temperature standards) and things that were hot (again by room temperature standards) I do not deny.

But consider taking some of that snow and putting it over a fire (since Anaximander could produce heat but not refrigeration we’ll have to make this a unidirectional experiment). He would see it turn into water and then, depending on the outside temperature, either simply disappear or turn into a haze in the air.

How would anyone of the time have described what was happening (remember that these people have no way of recording a temperature for later comparison with other temperatures and, indeed, no concept of the difference between heat and temperature)?

I could see someone describing it in accordance with a spectrum from hard to soft (or, if you prefer, cold to soft). I could see a spectrum from cold to comfortable to uncomfortable. I could see a spectrum from white to clear to invisible. Or dry to wet to invisible. All of these represent a report by an observer using his or her senses. You can *feel* it moving from cold to soft. You can *see* it moving from white to clear.

In contrast, moving from cold to somthing called hot is completely abstract until Fahrenheit, Celsius, Reaumur and friends devised scales to allow comparison: “that snow we found yesterday is ‘colder’ than the water in the stream we walked through this afternoon.”

“moving from cold to something called hot is completely abstract”

The abstract notion is surely the term “opposite”, and not the choice of the states to which it is applied. In what sense is dark the opposite of light, or hard the opposite of soft, other than in terms of the absence of one member of the chosen pair? In that case, soft becomes the absence of hard, dark the absence of light and cold the absence of heat. The context in which this (philosophical) comparison was made may well have been a purely domestic one, and so the absence of heat from a fire that has burned out, would have been an adequate illustration of heat’s opposite state, “absence of heat”, called “cold.”

In terms of “recording … for later comparison”, how would one measure relative hardness, I wonder? Perhaps by placing a piece of butter outside at midday and, regularly, testing the degree to which it becomes less hard over a given period of time, until it becomes completely liquid. One could then use the scale as a type against which to test the hardness of other substances with some degree of accuracy: “This honey is as hard as butter at midday plus 100 drips (of the clepsydra).” In a similar way, the degree of hotness of a fire might be measured by placing a straw into it at regular intervals and measuring how quickly it ignites (another method, assumimg a good supply of slaves or felons, would be to have one of them thrust a hand into the fire so that the length of time taken for the slave to pass out in pain can be measured. This would have the disadvantages, though, that a) there might be considerable variability in the slaves’ tolerance to pain and so some degree of inaccuracy in the results and b) the inconvenience of having always to carry a supply of slaves around.

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The author of this blog used to be an employee of Nortel. Even when he worked for Nortel the views expressed in the blog did not represent the views of Nortel. Now that he has left, the chances are even smaller that his views match those of Nortel.
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